/*
  KeePass Password Safe - The Open-Source Password Manager
  Copyright (C) 2003-2017 Dominik Reichl <dominik.reichl@t-online.de>

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

using System;
using System.Collections.Generic;
using System.Xml;
using System.Diagnostics;

using KeePassLib.Utility;

namespace KeePassLib
{
  // [ImmutableObject(true)]
  /// <summary>
  /// Represents an UUID of a password entry or group. Once created,
  /// <c>PwUuid</c> objects aren't modifyable anymore (immutable).
  /// </summary>
  public sealed class PwUuid : IComparable<PwUuid>, IEquatable<PwUuid>
  {
    /// <summary>
    /// Standard size in bytes of a UUID.
    /// </summary>
    public const uint UuidSize = 16;

    /// <summary>
    /// Zero UUID (all bytes are zero).
    /// </summary>
    public static readonly PwUuid Zero = new PwUuid(false);

    private byte[] m_pbUuid = null; // Never null after constructor

    /// <summary>
    /// Get the 16 UUID bytes.
    /// </summary>
    public byte[] UuidBytes
    {
      get { return m_pbUuid; }
    }

    /// <summary>
    /// Construct a new UUID object.
    /// </summary>
    /// <param name="bCreateNew">If this parameter is <c>true</c>, a new
    /// UUID is generated. If it is <c>false</c>, the UUID is initialized
    /// to zero.</param>
    public PwUuid(bool bCreateNew)
    {
      if (bCreateNew) CreateNew();
      else SetZero();
    }

    /// <summary>
    /// Construct a new UUID object.
    /// </summary>
    /// <param name="uuidBytes">Initial value of the <c>PwUuid</c> object.</param>
    public PwUuid(byte[] uuidBytes)
    {
      SetValue(uuidBytes);
    }

    /// <summary>
    /// Create a new, random UUID.
    /// </summary>
    /// <returns>Returns <c>true</c> if a random UUID has been generated,
    /// otherwise it returns <c>false</c>.</returns>
    private void CreateNew()
    {
      Debug.Assert(m_pbUuid == null); // Only call from constructor
      while (true)
      {
        m_pbUuid = Guid.NewGuid().ToByteArray();

        if ((m_pbUuid == null) || (m_pbUuid.Length != (int)UuidSize))
        {
          Debug.Assert(false);
          throw new InvalidOperationException();
        }

        // Zero is a reserved value -- do not generate Zero
        if (!Equals(PwUuid.Zero)) break;
        Debug.Assert(false);
      }
    }

    private void SetValue(byte[] uuidBytes)
    {
      Debug.Assert((uuidBytes != null) && (uuidBytes.Length == (int)UuidSize));
      if (uuidBytes == null) throw new ArgumentNullException("uuidBytes");
      if (uuidBytes.Length != (int)UuidSize) throw new ArgumentException();

      Debug.Assert(m_pbUuid == null); // Only call from constructor
      m_pbUuid = new byte[UuidSize];

      Array.Copy(uuidBytes, m_pbUuid, (int)UuidSize);
    }

    private void SetZero()
    {
      Debug.Assert(m_pbUuid == null); // Only call from constructor
      m_pbUuid = new byte[UuidSize];

      // Array.Clear(m_pbUuid, 0, (int)UuidSize);
#if DEBUG
      List<byte> l = new List<byte>(m_pbUuid);
      Debug.Assert(l.TrueForAll(bt => (bt == 0)));
#endif
    }

    [Obsolete]
    public bool EqualsValue(PwUuid uuid)
    {
      return Equals(uuid);
    }

    public override bool Equals(object obj)
    {
      return Equals(obj as PwUuid);
    }

    public bool Equals(PwUuid other)
    {
      if (other == null) { Debug.Assert(false); return false; }

      for (int i = 0; i < (int)UuidSize; ++i)
      {
        if (m_pbUuid[i] != other.m_pbUuid[i]) return false;
      }

      return true;
    }

    private int m_h = 0;
    public override int GetHashCode()
    {
      if (m_h == 0)
        m_h = (int)MemUtil.Hash32(m_pbUuid, 0, m_pbUuid.Length);
      return m_h;
    }

    public int CompareTo(PwUuid other)
    {
      if (other == null)
      {
        Debug.Assert(false);
        throw new ArgumentNullException("other");
      }

      for (int i = 0; i < (int)UuidSize; ++i)
      {
        if (m_pbUuid[i] < other.m_pbUuid[i]) return -1;
        if (m_pbUuid[i] > other.m_pbUuid[i]) return 1;
      }

      return 0;
    }

    /// <summary>
    /// Convert the UUID to its string representation.
    /// </summary>
    /// <returns>String containing the UUID value.</returns>
    public string ToHexString()
    {
      return MemUtil.ByteArrayToHexString(m_pbUuid);
    }

#if DEBUG
    public override string ToString()
    {
      return ToHexString();
    }
#endif
  }

  [Obsolete]
  public sealed class PwUuidComparable : IComparable<PwUuidComparable>
  {
    private byte[] m_pbUuid = new byte[PwUuid.UuidSize];

    public PwUuidComparable(PwUuid pwUuid)
    {
      if (pwUuid == null) throw new ArgumentNullException("pwUuid");

      Array.Copy(pwUuid.UuidBytes, m_pbUuid, (int)PwUuid.UuidSize);
    }

    public int CompareTo(PwUuidComparable other)
    {
      if (other == null) throw new ArgumentNullException("other");

      for (int i = 0; i < (int)PwUuid.UuidSize; ++i)
      {
        if (m_pbUuid[i] < other.m_pbUuid[i]) return -1;
        if (m_pbUuid[i] > other.m_pbUuid[i]) return 1;
      }

      return 0;
    }
  }
}
